Ugh.. 5.4.19 is more than five years old (Aug-2013), no security updates applied for two years (up to 5.4.45 in Sep-2015), end of life since then. Really, do yourself a favour and upgrade (better hosting providers offer different versions to choose from), PHP 7.2 (and 7.3 anyway) might be too fresh for s9y, but PHP 7.1 (7.1.28 current latest) works fine with s9y 2.1.4 and most other software meanwhile, but at least use PHP 5.6 with its latest security updates (5.6.40 current).

And there are others... Installing a more recent php version will affect all of these s9y installations for a specific domain. The only one I am having difficulty with is the one I just installed the latest s9y snapshot to, so I would like to discover the underlying problem to that specific installation prior to changing php versions unless my problem is well documented to exist as a result of php 5.4.

I'm quite certain that at least some new code will require a newer PHP version. I doubt any coder would cater to a platform that's EOL since 4 years and care for its restrictions unless being paid a significant amount of money or comparable goods.

With using a completely outdated PHP version you're exposing yourself, your hoster and maybe even your users to unnecessary risks that can be easily avoided by upgrading to a supported newer version that s9y is known to run on.